This invention relates to cross-linked elastomeric polyesters. More particularly, this invention relates to a method for preparing cross-linked elastomeric polyesters in latex form.
Linear, high molecular weight, aliphatic polyesters may be prepared by the polyesterification of aliphatic glycols with saturated dicarboxylic acids, or by the self-condensation of an hydroxy carboxylic acid. When a small portion of the glycol or carboxylic acid monomer contains ethylenic unsaturation, the resulting linear polyester contains a limited amount of ethylenic unsaturation. Polyester gums are generally vulcanizable with peroxides, and can be cured to form tough, oil-resistant elastomers. The including of a limited degree of unsaturation in the polyester serves to improve the rate of cross-linking and to lower the level of peroxide needed to accomplish the curing step. The preparation of polyesters as liquids or gums and subsequent vulcanization with a peroxide to form cured rubber articles or sheet stock is more fully described in U.S. Pat. No. 2,448,585.
The esterification or transesterification processes employed for the preparation of aliphatic polyesters are generally run in bulk or in solvents at elevated temperatures and essentially in the absence of water. The resulting high molecular weight polymer is a heavy liquid or gum which on curing becomes a solid, rubbery mass. Cured elastomeric polyesters have not been obtainable in a finely-divided particulate form such as a free-flowing powder or as a dispersed suspension or latex. Esterification processes do not lend themselves to being carried out in aqueous emulsion, and subjecting a cured rubber to a mastication or grinding process results in a non-uniform mixture of coarse rubber particles, rather than a finely-divided free-flowing powder.